Ion exchange resins are well known in the art. Typically, such resins are used as acid catalysts to synthesize various products. There is shown, for example, in U.S. Pat. No. 5,504,234 to Omura et al. the method for the preparation of (meth) acryloxyalkyl group-containing linear organopolysiloxanes. Instead of using a conventional acidic catalyst, the reaction is promoted by the use of a cation-exchange resin in the H+ form which is readily removed from the polymerization mixture after completion of the reaction. The catalytic efficiency of the cation-exchange resin is further enhanced if the resin is swollen with a polar organic solvent such as tetrahydrofuran prior to its use in the process.
There is shown in U.S. Pat. No. 5,315,042 to Cipullo et al. a process for making bisphenol-A utilizing an ion exchange resin catalyst and an optional free mercaptan promotor. Bisphenol-A is continuously prepared by reaction of phenol and acetone in the presence of an acidic catalyst under accelerated flow conditions with increased throughput in order to increase initial reactivity. The acetone and bisphenol-A are separated from the effluent stream prior to depletion of the acetone whereby the residence time of the bisphenol-A is reduced and undesirable by-products and color are reduced.
In U.S. Pat. No. 5,105,026 to Powell et al. there is shown another process for preparing bisphenol-A. In the '026 patent the process generally includes reacting a carbonyl compound with a stoichiometric excess of a phenolic compound in the presence of an acidic catalyst, crystallizing bisphenol-A and using an acidic ion exchange resin catalyst to convert at least a portion of the by-product to bisphenol.
Ion exchange resins are also typically used to remove undesirable ionic compounds from various media. For example, cationic resins are used in their sodium or hydrogen form to remove undesirable metallic ions from drinking water. So also, such resins are used in their acid (H.sup.+) form in like applications in organic media. Anionic resins, on the other hand, can be used to remove undesirable anions from various liquid media as is shown, for example, in U.K. Patent Application No. 2,112,394, published Jul. 20, 1983 of Becker et al. This patent relates to the removal of iodide compounds from acetic acid by using anionic ion exchange resins and reports efficiencies of up to approximately 90 percent.
There is also known in the art various processes which employ silver-exchanged cationic ion exchange resins for various purposes as further discussed below.
There is shown in U.S. Pat. No. 5,464,559 to Marchin et al. a composition for treating drinking water for the purpose of disinfecting the water and/or removing iodide. A chelating resin having iminodiacetate chelating groups is employed and the resin is loaded with not over 0.5 mol of silver ions per mol of iminodiacetate.
U.S. Pat. No. 5,220,058 of Fish et al. Discloses a process for removing iodides from carboxylic acids and/or carboxylic acid anhydrides. The process described involves using an ion exchange resin in which thiol functional groups have been exchanged with silver, palladium or mercury.
In U.S. Pat. No. 4,615,806 to Hilton there is shown a preferred method for removing iodide compounds from non-aqueous media, such as acetic acid. The media is contacted with a macroreticulated (macroporous), strong-acid cation exchange resin which has at least one percent of its active sites converted to the silver or mercury form. By way of the method of the '806 patent, iodide compounds, both organic iodides and ionic iodides are quantitatively removed from acetic acid in short contact times (on the order of 100 seconds). The resins of the present invention may be used in practicing the process of U.S. Pat. No. 4,615,806 in order to remove iodide compounds from non-aqueous media such as acetic acid and acetic anhydride at elevated temperatures.